Abbot Point in Bowen, Queensland is a gateway to the vast coal reserves of the Galilee Basin.

The Great Barrier Reef Marine Park Authority has approved a proposal to dump dredge spoil from the Abbot Point coal terminal expansion in the marine park area.

Three million cubic metres of spoil must be dredged as part of the project at Bowen in North Queensland green-lighted by Federal Environment Minister Greg Hunt last month.

Scientists and conservation lobbyists had urged the Authority to reject the expansion, with 233 signing a letter to chairman Russell Reichelt that said: "The best available science makes it very clear that expansion of the port at Abbot Point will have detrimental effects on the Great Barrier Reef. Sediment from dredging can smother corals and seagrasses and expose them to poisons and elevated nutrients."

Greenpeace warns that any dumping of dredge spoil on the World Heritage-listed reef will be an "international embarrassment" and akin to "dumping rubbish in the Grand Canyon".

"We wouldn't throw rubbish on World Heritage sites like the Grand Canyon or the Vatican City, so why would we dump on the reef?" spokeswoman Louise Matthiesson said.

"Scientists are clear that the potential impacts of dumping the dredge spoil so close to fringing reefs and the WWII Catalina plane wreck are significant."

What the expansion involves

The Abbot Point expansion will create one of the world's biggest coal ports, located about 25 kilometres north of Bowen on the central Queensland Coast and handling exports for companies mining the vast coal reserves of the Galilee Basin.

Various conglomerates, including Australia's own Gina Rinehart and Clive Palmer, are negotiating leases for the area.

According to the Great Barrier Reef Marine Park Authority, the area to be dredged is located about three kilometres offshore of Abbot Point and is "wholly contained within existing port limits of Abbot Point".

The dredging of "previously undisturbed seabed" is required to deepen an area around six new ship berths as part of the development of Terminal 0, Terminal 2 and Terminal 3.

While the area to be dredged is located within the Great Barrier Reef World Heritage Area, it is in an area excluded from the marine park.

Strict conditions, but are they enough?

Announcing the expansion in December, Mr Hunt said he was imposing strict environmental conditions on the project.

"It is my intention that the first priority for all future capital dredging projects within the central and north Queensland coastal zone will be for shoreline, near-to-shore or land reclamation disposal," he said.

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"This follows my recent agreement with the Gladstone Ports Authority that they will not dispose of up to 12 million cubic metres of spoil within the marine park, but will instead use this material for land infill.

"This is a significant step towards improving and protecting the marine park for future generations."

Mr Hunt said one condition would be that any dredging would be limited to 1.3 million cubic metres of sediment a year and conducted during a "small window" nominated by environmental scientists.

He also said that he would demand "a 150 per cent net benefit requirement for water quality" in the reef area, a target that Wendy Tubman from the North Queensland Conservation Council said was unachievable.

"You've got water of a certain clarity, then you add three million cubic metres of dredge spoil, finds, sands, sludge," she said.

"Now I don't know about you, but I can't see how that's going to improve water quality."

Jon Brodie, a senior researcher at James Cook University, told ABC News Online that while the Federal Government had limited estimations of dredge spoil from the project to three million cubic metres, the effects would be "cumulative" and set a precedent for other developments along the Queensland coast.

Citing projects at major ports along the Great Barrier Reef coast - including in Cairns, Townsville, Hay Point (Mackay) and Gladstone - that could create as much as 80 million cubic metres of spoil, he said: "It will add to the destruction of a system that is already going downhill badly."

And over the next decade more dredging would be needed at Abbot Point to make room for future exports from Waratah Coal's Alpha North project, he added.

Is there an alternative to dumping spoil on the reef?

In announcing the expansion in December, Mr Hunt said the Government preferred that where possible, spoil from dredging be used as infill for land reclamation.

"There are great examples in Queensland where the material produced by dredging has been used for land reclamation - for example, the Port of Brisbane," he said in a statement.

Mr Brodie, who has outlined alternatives in an article published on The Conversation website, says that among "several options" for disposal of dredge spoil are building a retaining barrier, called a bund wall, like that used at Gladstone Harbour, adding that in the case of Abbot Point, "I really can't understand why that's not on the table".

However, unlike the wall at Gladstone, which the local ports authority has admitted leaked sediment into the harbour in 2011 and 2012, it would need to be "done properly".

"This would also have the benefit of increasing port land, an important consideration at Abbot Point as useable land is scarce," he wrote.

Another option was to build longer jetties, he added, reducing the need for dredging.

"The emphasis should be on designing ports in ways that safeguard the Great Barrier Reef, rather than causing damage and then trying to fix it," he wrote.

Among the 95 environmental conditions on the Abbot Point project, the Minister states a requirement for "identification of alternative disposal sites for analysis", although disposal at an alternative site will only be allowed "if it would have the equivalent or lesser impacts than the site".

Business groups, meantime, have applauded the Government's decision to allow the expansion of the port.

Bowen Chamber of Commerce chairman Bruce Heddich said: "Bowen, being adjacent to Abbot Point, is the real winner in this decision. It can only go well for the future of the town."